In a pump of the above-mentioned type disclosed in German patent application No. 32 48 364, the inlet and outlet valves are configured as spherical seat valves, and the valve seat is respectively provided by a stepped expansion of the valve bore in the pump housing. Structural provisions for a simple manufacture of the valve bore and for an easy assembly and testing of the valves are not disclosed in the said application. The pump includes a piston as a displacement element which is guided and sealed in a cylinder bore that crosses the valve bore and is drivable by an eccentric in the pressure direction and by a spring in the suction direction.
German patent application No. 40 27 848 discloses a piston pump wherein the inlet valve and the outlet valve are respectively arranged in a separate stepped bore which is connected to the working chamber by way of a connecting bore. The inlet and outlet vales are provided by different valve inserts which comprise the stationary valve seat, the movable closing element and a valve spring. This prior art piston pump necessitates machining of the stepped bores and the installation of the valve inserts from opposite sides of the pump housing. This has unfavorable effects on manufacturing costs and implies a great restriction of the design possibilities of a constructor, for example, in terms of a structural integration of the pump housing in the housing of a valve block.
An object of the present invention is to provide a pump of the above-mentioned type which involves low efforts and expenditure in manufacture and assembly and can easily be integrated into the housing of a hydraulic unit.
According to the present invention, this object is achieved because the valve seat, the closing element and a valve spring of the inlet valve or the outlet valve, which spring presses the closing element against the valve seat, are interconnected to form a cartridge which is adapted to be sealedly installed into the valve bore, and the cartridges of both valves can be fitted from the same side into the valve bore and are adapted to be supported on the pump housing in the installation direction by means of a step in the valve bore. If the construction of the pump permits it, the cartridges of both valves may further be supported on each other. Besides, in a particularly simple embodiment of the present invention, the valve seat, the closing element and the valve spring of the inlet valve and outlet valve may be interconnected to form one single cartridge which can be sealedly inserted into the valve bore.
It is advantageous in the design of the pump according to the present invention that the valve bore can be fabricated in one single operation and, exactly as the assembly of the valves, can be effected from one side of the pump housing. Also, the assembly of the valves can be carried out in one single operation, provided their cartridges are not spaced from one another. This reduces the manufacturing costs and simplifies the accommodation of the pump in a housing provided for further structural elements. In addition, it is a special advantage that the valves in the preassembled cartridges can be tested prior to their installation so that defects of fabrication can be detected early and installation of defective parts can be avoided. If both valves, i.e., the inlet valve and the outlet valve, are accommodated in one joint cartridge, it is possible to remarkably reduce the number of the valve components and the mounting space required.
According to the present invention, the cartridge can be assembled of several parts. The cartridge may include a housing or a housing part made of a material of reduced rigidity, for example, aluminum or free cutting steel, which is connected to a valve seat ring made of a material of higher rigidity, for example, hardened steel. The cartridge may be retained and sealed in the valve bore in different fashions. One favorable type of attachment is caulking the cartridge into the valve bore. Preferably, the cartridge or the cartridges is/are inserted into the valve bore from the high-pressure side end so that the valves, in their closed position, are acted upon by the pump pressure in the installation direction in which they are supported on the pump housing by way of a step in the valve bore. The cartridges may be sealed metallically by correspondingly shaped seat surfaces or by means of ring seals. According to the present invention, a particularly favorable attachment and sealing can be achieved in that the end of the cartridge, which is the rear end when viewed in the installation direction, has a sleeve-type portion, and by pressing a plug into the sleeve-type portion, the latter is expandable and thereby adapted to be attached in the valve bore in operative and sealed engagement therewith.
When the pump has a damping chamber which succeeds the outlet valve, it is favorable that the cartridge is installed from the damping chamber. To fix the cartridge or the cartridges in the installation position, a compression spring can be used which is mounted into the damping chamber and is supported on the end of the cartridge that projects into the damping chamber.